Wikipedia, the encyclopedia that relies on volunteers to pen nearly 4 million articles, is about as accurate in covering scientific topics as Encyclopedia Britannica, the journal Nature wrote in an online article published Wednesday.
The finding, based on a side-by-side comparison of articles covering a broad swath of the scientific spectrum, comes as Wikipedia faces criticism over the accuracy of some of its entries.
Two weeks ago prominent journalist John Seigenthaler Sr. revealed that a Wikipedia entry that ran for four months had incorrectly named him as a longtime suspect in the assassinations of president John F. Kennedy and his brother Robert.
Such errors appear to be the exception rather than the rule, Nature said in Wednesday's article, which the scientific journal said was the first to use peer review to compare Wikipedia to Britannica. Based on 42 articles reviewed by experts, the average scientific entry in Wikipedia contained four errors or omissions, while Britannica had three.
Of eight "serious errors" the reviewers found — including misinterpretations of important concepts — four came from each source, the journal reported.
"We're very pleased with the results and we're hoping it will focus people's attention on the overall level of our work, which is pretty good," said Jimmy Wales, who founded St. Petersburg, Fla.-based Wikipedia in 2001.
Wales said the accuracy of his project varies by topic, with strong suits including pop culture and contemporary technology. That's because Wikipedia's stable of dedicated volunteers tend to have more collective expertise in such areas, he said.
The site tends to lag when it comes to topics touching on the humanities, such as the winner of the Nobel Prize for literature for a particular year, Wales said.
Next month, Wikipedia plans to begin testing a new mechanism for reviewing the accuracy of its articles. The group also is working on ways to make its review process easier to use by people who have less familiarity with computers and the Internet.
Encyclopedia Britannica officials declined to comment on the findings because they haven't seen the data. But spokesman Tom Panelas said such comparisons, assuming they're conducted correctly, are valuable "because they tell us things you wouldn't know otherwise."
While some Britannica officials have publicly criticized Wikipedia's quality in the past, Panelas praised the free service for having the speed and breadth to keep up on topics such as "extreme ironing." The sport, in which competitors iron clothing in remote locations, is not covered in Britannica.
Britannica researchers plan to review the Nature study and correct any errors discovered, Panelas said.
Unlike Britannica, which charges for its content and pays a staff of experts to research and write its articles, Wikipedia gives away its content for free and allows anyone — amateur or professional, expert or novice — to submit and edit entries.
Wikipedia, which boasts 3.7 million articles in 200 languages, is the 37th most visited Web site on the Internet, according to the research service Alexa.